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Abstract

Incidence of cerebrovascular disease is higher in men than in age-matched premenopausal women. Stroke-related diseases may involve oxidative stress due to augmented generation of superoxide from NADPH oxidase. However, it is unknown if there are gender differences in NADPH oxidase in the cerebral circulation. We tested the hypothesis that female gender is associated with lower NADPH oxidase activity, expression and function in the cerebral circulation, and that any differences are dependent on the female sex hormone, estrogen. NADPH-stimulated superoxide production by cerebral arteries (basilar, BA; middle cerebral, MCA) from SD rats of both genders was measured by lucigenin-enhanced chemiluminescence or dihydroethidium. Vascular responses of BA to NADPH were assessed in a myograph. Protein expression of the NADPH oxidase catalytic isoforms Nox1, Nox2 and Nox4 was compared between male and female cerebral arteries using western blotting. Some female rats were ovariectomized (OVX) and treated with either vehicle or 17b-estradiol (10 ug/kg/d) for 14 d post-OVX. NADPH-stimulated superoxide production by BA and MCA from intact female rats was ~50% of the levels generated by male cerebral arteries (P<0.05). NADPH-stimulated superoxide production was inhibited by the NADPH oxidase inhibitors, diphenyleneiodonium (5mM), apocynin (0.3mM) or gp91ds-tat (1uM). NADPH (10 –100uM) relaxed precontracted BA from both female and male rats, however, relaxations were selectively ~50 % smaller in females (P<0.05). The H2O2 scavenger, catalase (1000 U/mL), prevented NADPH-induced relaxations in BA from both genders. Expression of Nox1 and Nox4 was ~2-fold higher in males than in females, whereas Nox2 expression was ~2-fold higher in females than in males. NADPH-stimulated superoxide production by BA and MCA from OVX rats treated with vehicle was 2 to 4-fold greater than levels in intact females (P<0.05). Treatment of OVX rats with 17b-estradiol decreased both superoxide production (P<0.01) and NADPH-induced BA relaxations to levels similar to those in male vessels. Thus, NADPH oxidase activity and function is lower in cerebral arteries from female rats and that these gender differences are estrogen-dependent and likely due to Nox1 and/or Nox4 activity.